1. Field of the Invention
The present invention relates to a cold cathode flat fluorescent lamp (CCFFL), and more particularly to a patterned electrode of a CCFFL.
2. Description of the Related Art
With the advance of technology, digital devices, such as mobile phones, digital cameras, digital video cameras, notebooks, and desktops are developed to have convenience, multiple functions and attractive designs. Display monitors of mobile phones, digital cameras, digital video cameras, notebooks, and desktops are essential interfaces between users and devices. Through the display monitors, users can conveniently use the devices. In recent years, display monitors of mobile phones, digital cameras, digital video cameras, notebooks, and desktops are liquid crystal display (LCD) panels, which, however, are not self-luminant. Therefore, a back-light module is disposed under a LCD panel to provide a light source to achieve the display purpose.
Having good luminance efficiency and uniformity, and the ability to provide a large-scale light source, the cold cathode flat fluorescent lamp (CCFFL) has been widely applied to the back-light module of LCD panels and other fields. A CCFFL is a plasma luminance device. By emitting electrons from a cathode to collide with inert gas between a cathode and an anode within a flat lamp chamber, the inert gas is ionized and excited to generate plasma. The excited atoms of the plasma return to the ground state by radiating ultra-violate (UV) light. The UV light then excites fluorescent substance in the CCFFL to generate visible light.
FIG. 1 is a schematic drawing showing a conventional CCFFL. Referring to FIG. 1, the conventional CCFFL comprises a flat lamp chamber 100, fluorescent substance 102, discharge gas 104, a patterned electrode 106, and a dielectric layer 108. Wherein, the flat lamp chamber 100 comprises flat substrates 100a and 100b, and edge stripes 100c. The edge stripes are disposed between the flat substrates 100a and 100b, and connect with the edges of the flat substrates 100a and 100b to form a sealed chamber.
Referring to FIG. 1, the material of the conventional patterned electrode 106 is usually silver, and the patterned electrode 106 is disposed over the flat substrate 100a. Usually, the dielectric layer 108 covers the patterned electrode 106 to protect the patterned electrode 106 from damage from ion collision. From FIG. 1, it is known that the patterned electrode 106 and the dielectric layer 108 thereon are on the inner wall of the flat lamp chamber 100. The discharge gas 104 is then injected in the flat lamp chamber 100. Usually, the discharge gas 104 is Xe, Ne, Ar, or other inert gas. In addition, the fluorescent substance 102 is disposed on the inner wall of the flat lamp chamber 100, for example, on the surface of the flat substrate 100b, the surface of the dielectric layer 108, and the surface of the flat substrate 100a, which is not covered by the dielectric layer 108, for example.
When the CCFFL is lit up, electrons emitted from the patterned electrode 106 collide with the discharge gas 104 in the flat lamp chamber 100 so that the discharge gas 104 is ionized to generate plasma. The excited atoms of the plasma return to the ground state by radiating UV light. The UV light then excites the fluorescent substance 102 on the inner wall of the flat lamp chamber 100 to generate visible light. In the luminance mechanism described above, however, the high-energy ions of the plasma would penetrate the dielectric layer 108 and damage the patterned electrode 106. As a result, the life time of the CCFFL is substantially reduced.
FIG. 2 is a schematic drawing showing a patterned electrode of a conventional CCFFL. Referring to FIG. 2, the patterned electrode of the conventional CCFFL comprises a plurality of meandering anodes 210, and a plurality of meandering cathodes 220. Because the meandering anodes 210 and the meandering cathodes 220 have sin-waveform designs, ideally, the meandering anodes 210 and the meandering cathodes 220 generate plasma in the luminance areas 230a and 230b. However, the luminance areas 230a and 230b are driven by the same meandering cathode 220 so that the luminance area 230a is lit up, but the luminance area 230b is not. In other words, sharing the same meandering cathode 220 or the same meandering anode 210 usually means only one of the two sides of the meandering cathode 220 or the meandering anode 210 is lit up. As a result, a dark-bright pattern would appear on the CCFFL, thus deteriorating the uniformity of the light source.